This invention relates to a composition and method for alleviating neuropathic pain. More particularly, this invention is directed to a composition and method for alleviating neuropathic pain in which a neuropathic pain-alleviating amount of an anticonvulsant is combined with an anticonvulsant-potentiating amount of a nontoxic antagonist, or blocker, for the N-methyl-D-aspartate (NMDA) receptor or nontoxic substance that blocks a major intracellular consequence of NMDA receptor activation.
Neuropathic pain is pain that is due to functional abnormalities of the nervous system. Fields, "Pain", McGraw-Hill, Inc. (1987), pp. 133 et seq. There are a variety of possible mechanisms by which nerve dysfunction can cause neuropathic pain: hyperactivity in primary afferent or central nervous system (CNS) nociceptive neurons, loss of central inhibitory connections, and increased activity in sympathetic efferents. Neuropathic pain typically occurs following injury to elements of i:he nervous system involved in nociception, such as peripheral nerve injury, in which the lesions deafferent the nociceptive pathway, the resultant pain sometimes being referred to deafferentation pain. Neuropathic pain is much more likely to occur with peripheral than with central nervous system damage. Examples of causes of painful nerve injury are: accidental trauma, tumors, cerval or lumbar spine disease, and surgical procedures. These injuries usually involve one or two peripheral nerves or nerve roots, and the pain is felt in the body region normally innervated by the damaged nerves. Additionally, there are also toxic, metabolic, and hereditary causes of painful polyneuropathies, e.g., alcohol abuse, diabetes mellitus. These tend to be symmetrical and are most severe on the distal limbs.